OMC 5.0 L EFI 1993 idle surge problem Still Unsolved.

[93fourwinnshorizon2]

I posted this a couple of years ago and still working on the same problem with no solution. One mechanic blamed the ethanol in gas and suggested ValveTec additive. That didn't work either.
This will be the fourth season with this problem. :facepalm:

OMC 5.0L EFI Idle surge problem
I have an 1993 OMC 5.0L EFI 200 HP I/O that is garage kept when not in use. The boat has been trouble free until this perplexing problem.

The boat starts up and runs great and idles well and runs perfectly under load and operates at normal temps. (needle is in the middle of the guage. Never had overheating issue.)
When the motor is shut off after running at normal operating temps, everything is normal. I'll let it sit for at least 2 minutes and when I start it again while it's warm, the idle will surge until it eventually dies.
The computer is trying to compensate for the surging. Surge will go up to 1700 RPM, it does eventually die. If I start it up and put it into gear, it will run fine until I put it back into neutral. It will then go into the idle surge cycle.
If I let the motor cool for a few hours or overnight, the boat starts up idles perfectly again. If I shut it off and let it sit, and try again, the idle surge cycle continues. Gas is fresh and changed over a few times, tried STP gas treatment too.
I even drained the boat gas tank into the family car. Car ran fine.

I brought it into the shop and did a full tune up, and hooked it up to the computer with no error codes.
I changed out the IAC valve, temp sensor,water sensor and high pressure fuel pump, impellar. I even connected up a 5 gallon tank to isolate boat gas tank to eliminate that variable. Same surge.

All filters have been changed and even drained the gas tank to ensure it's water free. I thought about attacking the risers to see if they are clear and blockage free.

If you are an OMC owner and had this problem and resolved it, please share a possible solution.

Thank you for your time.

 

[muc]

Re: OMC 5.0 L EFI 1993 idle surge problem Still Unsolved.

When you say all filters do you mean all or just the fuel filter?
Did you replace or remove the filter under the IAC?
Have you gone thru the VST and checked the float and needle + seat?
Checked PVC filter?
Checked pulse limiter?
Checked the MAP filter?
Might want to compare fuel pressure when its running right verse when its surging.

 

[Black as]

Re: OMC 5.0 L EFI 1993 idle surge problem Still Unsolved.

I posted this a couple of years ago and still working on the same problem with no solution. One mechanic blamed the ethanol in gas and suggested ValveTec additive. That didn't work either.
This will be the fourth season with this problem. :facepalm:

OMC 5.0L EFI Idle surge problem
I have an 1993 OMC 5.0L EFI 200 HP I/O that is garage kept when not in use. The boat has been trouble free until this perplexing problem.

The boat starts up and runs great and idles well and runs perfectly under load and operates at normal temps. (needle is in the middle of the guage. Never had overheating issue.)
When the motor is shut off after running at normal operating temps, everything is normal. I'll let it sit for at least 2 minutes and when I start it again while it's warm, the idle will surge until it eventually dies.
The computer is trying to compensate for the surging. Surge will go up to 1700 RPM, it does eventually die. If I start it up and put it into gear, it will run fine until I put it back into neutral. It will then go into the idle surge cycle.
If I let the motor cool for a few hours or overnight, the boat starts up idles perfectly again. If I shut it off and let it sit, and try again, the idle surge cycle continues. Gas is fresh and changed over a few times, tried STP gas treatment too.
I even drained the boat gas tank into the family car. Car ran fine.

I brought it into the shop and did a full tune up, and hooked it up to the computer with no error codes.
I changed out the IAC valve, temp sensor,water sensor and high pressure fuel pump, impellar. I even connected up a 5 gallon tank to isolate boat gas tank to eliminate that variable. Same surge.

All filters have been changed and even drained the gas tank to ensure it's water free. I thought about attacking the risers to see if they are clear and blockage free.

If you are an OMC owner and had this problem and resolved it, please share a possible solution.

Thank you for your time.

I would try cleaning out the throttle body with throttle body cleaner comes in a spray can and the instructions are on the can and also checking for any air leaks.

 

[93fourwinnshorizon2]

Re: OMC 5.0 L EFI 1993 idle surge problem Still Unsolved.

When you say all filters do you mean all or just the fuel filter?
Did you replace or remove the filter under the IAC?
Have you gone thru the VST and checked the float and needle + seat?
Checked PVC filter?
Checked pulse limiter?
Checked the MAP filter?
Might want to compare fuel pressure when its running right verse when its surging.

Thanks you've responded with some excellent suggestions and it demonstrates that you read my situation and thought carefully about responding. I really appreciate your feedback.
The IAC was replaced and same problem. I cleaned the metal "frit" filter under the IAC last season. Same problem. I'll check out the other items. I know nothing of the PVC filter or the MAP filter, and will learn shortly.

My mechanic really believes it's a fuel and heat problem. I think he's right about the heat because it only happens when the engine is warm....after shutting down and starting up. I can let the motor run all day and it will run great. Shut it down for a minute, start it up and the surge starts. Under power, no problems. Put it in neutral, the surge starts within 10 seconds.

 

[figaro]

Re: OMC 5.0 L EFI 1993 idle surge problem Still Unsolved.

reading through the posts above id be looking at fuel pressure specs , also bleed down of pressure once shut down (possible leaky injector(s), fuel pressure regulator diaphram leaking fuel into vac line and go over every ground to make sure they are clean and tight

 

[93fourwinnshorizon2]

Re: OMC 5.0 L EFI 1993 idle surge problem Still Unsolved.

Problem Solved.

The Mustang Forums have blogging about this "surge demon" for years. Ford had a recall on the issue in 1994 and had a fix using the part in the link below. I've had this surge for five seasons now and 4 separate boat shops and countless of boat mechanics. I talked to a couple of Ford mechanics in the past two weeks and they recall this surge from that era motor.
Stupid me, why didn't I search the Mustang blogs in the first place. Every part on the OMC block has Ford Mustang DNA. I documented my problem here and the feedback became a wild goose chase.

I'm now going through this checklist to see if I overlooked a sensor.

http://www.stangnet.com/mustang-forums/698148-help-me-create-surging-idle-checklist.html

I purchased this device that was listed on an old Ford recall from 1994.
For $50 bucks it's worth a try as nothing else has worked.

http://k-mansparts.com/items/perfor...e-idle-spacer-kit-50-46-f2pz9f939a-detail.htm



The part was easy to install. While the IAC was off, I cleaned the noise supression filter that is fitted inside the adaptor. (I clean this filter every year with carb cleaner as air passes through it.) The motor makes an awfully loud sucking sound if that's not in place so the name of the part says it all.

I put everything back together and started it up. Idle when cold was 900 RPM and 700 when warm. I let it run in the driveway for a good 20 minutes so it was warmed up nicely. Shut it off for few minutes. Started it up and let it run 5 minutes. NO SURGE YAHOO!!!!!!.
I repeated the cycle a few times at various times. NO SURGE. OH THANK YOU K-Man and the Mustang Forums.

I started to play with the set screws on the plate and was able to hear the surge demon coming when I closed one of the set screws completely. I backed it off until the engine ran smooth. RPM was between 700-800.

When the Chicago winter finally breaks after Memorial Day, I'll get it in the water as the final test. At this very moment, I'm thrilled to have a solution. No more Idle Surge.

 

[Justin Kennedy]

Re: OMC 5.0 L EFI 1993 idle surge problem Still Unsolved.

Is the problem still solved? I am going through this same problem